Ohm Symbol
About Ohm Symbol
Ω is the ohm symbol, representing the unit of electrical resistance in the International System of Units, named after German physicist Georg Simon Ohm. The ohm symbol Ω is fundamental in electrical engineering and physics, measuring how strongly a material resists electric current flow, often paired with the micro symbol µ for precision measurements.
The ohm symbol Ω is visually identical to the uppercase Greek letter omega, shaped like an upside-down U with feet. As a Unicode character, the ohm symbol holds codepoint U+2126 within the Letterlike Symbols block. The ohm symbol is distinct from the infinity symbol ∞, which is a horizontal figure-eight rather than an omega shape.
【Historical Origin】 Georg Ohm discovered the relationship between voltage, current, and resistance in 1827, formulating Ohm's Law. The ohm symbol Ω was officially adopted for resistance measurement in 1881 at the International Electrical Congress, chosen because omega is the last letter of the Greek alphabet, symbolizing completeness in electrical theory.
【Modern Applications】 Today the ohm symbol Ω is ubiquitous in electronics, often paired with the micro symbol µ in µΩ (micro-ohm) measurements for high-precision applications. The lowercase sigma σ represents conductivity—the inverse of resistance measured by the ohm symbol. Resistance values from milliohms to megaohms use the ohm symbol in circuit design and component specification.
How to Type Ohm Symbol
Windows Input
Method 1: Hold Alt and type 8486 on the numeric keypad; Method 2: Type oumu in Chinese input method; Method 3: Use Character Map to copy the ohm symbol.
Mac Input
Method 1: Press Option + Z to directly type the ohm symbol Ω; Method 2: Press Control + Command + Space and search "ohm" or "omega"; Method 3: Use the Greek keyboard for uppercase omega as the ohm symbol.
HTML/CSS Input
HTML: Ω or Ω or Ω; CSS: content: "\2126";
LaTeX Input
Use \Omega for the ohm symbol Ω in LaTeX math mode. For text mode electrical units, use the siunitx package with \ohm for proper ohm symbol rendering in circuit documentation.
Ohm Symbol FAQ
What does the ohm symbol Ω measure in electricity?
The ohm symbol Ω measures electrical resistance—how much a material opposes current flow. One ohm equals the resistance when one volt produces one ampere of current, as described by Ohm's Law: V = IR, where R uses the ohm symbol for units.
How is the ohm symbol used with the micro symbol?
The micro symbol µ combines with the ohm symbol Ω to form µΩ (micro-ohm), measuring extremely low resistance in high-current applications. This pairing of the micro symbol and ohm symbol is essential in precision electrical engineering for power transmission systems.
Is the ohm symbol the same as the infinity symbol?
No, the ohm symbol Ω (uppercase omega) looks like an upside-down U with feet, while the infinity symbol ∞ is a horizontal figure-eight. The ohm symbol measures electrical resistance; the infinity symbol represents endlessness—they are entirely different characters.
How does the ohm symbol relate to lowercase sigma in physics?
Lowercase sigma σ represents electrical conductivity, which is the mathematical reciprocal of resistivity measured by the ohm symbol Ω. Higher conductivity (lowercase sigma) means lower resistance (ohm symbol), making them inversely related in electrical physics.